Flaxseed

Overview

Flaxseed, or linseed (Linum usitatissimum L.), comes from the flax plant, which is an annual herb. The ancient Egyptians used flaxseed as both food and medicine. In the past, flaxseed was used mostly as a laxative. It is high in fiber and contains a gummy material called mucilage, both of which expand when they come in contact with water. They add bulk to stool and help it move more quickly through the intestines.

Flaxseed and flaxseed oil are rich in alpha-linolenic acid (ALA), an omega-3 fatty acid that may be helpful for heart disease, inflammatory bowel disease (IBD), arthritis, and other health problems. Other omega-3 fatty acids include those found in fish oil, which are docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). Mackerel, salmon, and walnuts are good sources of omega-3 fatty acids.

Flaxseed oil contains only ALA, not the fiber or lignans found in the flaxseed. Other plants that contain ALA include canola (rapeseed), soybean oil, walnuts, and pumpkin seed. Studies suggest that flaxseed may help prevent and treat of the following health conditions.

High cholesterol

People who eat a Mediterranean diet tend to have higher HDL ("good") cholesterol levels. The Mediterranean diet includes whole grains, root and green vegetables, fruits, fish and poultry, olive and canola oils, and ALA from flaxseed, flaxseed oil, and walnuts. It limits the amount of red meat, butter, and cream you eat.

In lab tests and animal studies, flaxseed and flaxseed oil have been reported to lower cholesterol. Human studies have had mixed results. One human study found that people who added flaxseed to a low-cholesterol diet lowered their LDL ("bad") cholesterol and triglyceride levels (fats in the blood).

Heart disease

A diet rich in fruits, vegetables, whole grains, nuts or legumes, and foods with ALA may reduce the risk of heart attack and stroke, both for people who have never had either problem and for those who have already had a heart attack or a stroke.

One of the best ways to help prevent and treat heart disease is to eat a diet low in saturated fat and trans fat, and eat foods that are rich in monounsaturated and polyunsaturated fats, including omega-3 fatty acids from flaxseed. Evidence suggests that people who eat an ALA-rich diet are less likely to have a fatal heart attack.

Several human studies suggest that a diet rich in omega-3 fatty acids (including ALA) may lower blood pressure in people with hypertension.

Menopausal symptoms

One small study compared flaxseed to hormone replacement therapy (HRT) in menopausal women. It reported that 40 g of flaxseed worked as well as HRT for mild menopausal symptoms (hot flashes, mood disturbances, vaginal dryness). But the study was not well designed, and another, larger study found that flaxseed did not improve symptoms like hot flashes, nor did it protect against bone loss.

Breast cancer

Flaxseed contains phytoestrogens, which are plant chemicals called lignans. Because lignans may act like estrogen in the body, scientists aren't sure whether flaxseed would be harmful or helpful for breast cancer. Laboratory studies have reported that flaxseed reduced breast tumor growth and metastasis (spreading) in rats.

There has been only one clinical study in humans. In that study, postmenopausal women who were newly diagnosed with breast cancer ate a muffin with 25 grams dietary flaxseed every day for 40 days. The study found that adding flaxseed to the diet may have the potential to reduce tumor growth in women with breast cancer. But much more research is needed.

Colon cancer

Animal studies show that lignans may slow the growth of colon tumor cells. Population studies suggest that flaxseed may reduce the number of abnormal cell growths, which are early markers of colon cancer. Clinical trials in people are needed, however.

Prostate cancer

Results from studies are confusing when it comes to prostate cancer and flaxseed. A few studies seemed to show that ALA intake was associated with an increased risk for prostate cancer. But other studies have found that flaxseed may benefit men at risk for prostate cancer. In one study, men with a precancerous prostate condition called PIN had lower PSA levels (a marker of prostate cancer) when they ate 30 g of flaxseed daily along with a low-fat diet. In men who had prostate cancer, 30 g of flaxseed daily and a low-fat diet did not lower PSA levels. But it did appear to lower levels of testosterone and slow down the rate of tissue growth. More studies are needed to understand how flaxseed may affect prostate cancer.

Plant description

Flax is an annual plant that thrives in deep moist soils rich in sand, silt, and clay. The small, oval-shaped seeds of the flax plant contain oil, sometimes called linseed oil.

What's it made of?

Flaxseed has several plant chemicals that may be healthy, including:

Fiber, both soluble and insoluble

Protein

Essential fatty acids (ALA)

Lignans

Flaxseed acts like a laxative because of its fiber and mucilage content.

The health benefits of flaxseed, such as protection from heart disease and arthritis, are probably due to a high concentration of the omega-3 fatty acid ALA.

In addition to the important omega-3 fatty acid ALA, flaxseed -- not the oil -- also contains phytoestrogens, which are plant chemicals called lignans. Phytoestrogens act like the hormone estrogen and may help protect against some kinds of cancer.

Available forms

Flaxseed oil should be refrigerated. Use whole flaxseeds within 24 hours of grinding, otherwise the ingredients lose their activity. Flaxseeds are also available ground in a special mylar package so that the components in the flaxseeds stay active. Ripe seeds, linseed cakes, powder, capsules, and flaxseed oil are all available at health food and grocery stores.

How to take it

Pediatric

Flaxseed oil may be added to a child's diet to help balance fatty acids.

Children (2 to 12 years old): Ask your doctor to help you determine the right dose. One example is using 1 tsp of ground flaxseeds or 1 tsp of fresh flaxseed oil for constipation.

Adult

Flaxseed: Take 1 tbsp, 2 to 3 times daily, or 2 to 4 tbsp, 1 time daily. Grind before eating and take with lots of water.

Flaxseed oil: Take 1 to 2 tsp daily, or 1 to 2 capsules daily. Flaxseed oil is often used in a liquid form, which contains about 7 g of ALA per 15 mL tbsp.

Precautions

The use of herbs is a time-honored approach to strengthening the body and treating disease. Herbs, however, can have side effects and interact with other herbs, supplements, or medications. For these reasons, herbs should be taken with care, under the supervision of a health care provider qualified in the field of botanical medicine.

Although studies have found that eating fish -- which includes omega-3 fatty acids -- regularly may reduce the risk of macular degeneration, a recent study of two large groups of men and women found that diets rich in ALA may increase the risk of macular degeneration. Talk to your health care provider.

Do not eat raw or unripe flaxseeds -- they may be poisonous.

Women with breast, uterine, and ovarian cancer or endometriosis should ask their doctor before taking flaxseed, because it may act like estrogen in the body.

Some researchers think pregnant women shouldn't take flaxseed, because it may act like estrogen in the body. Ask your doctor before taking flaxseed if you are pregnant or breastfeeding.

Men with prostate cancer should ask their doctor before taking flaxseed.

People with a bowel obstruction, inflamed bowel, or narrowed esophagus should not take flaxseed. It is high in fiber and could make the condition worse.

If you take ground flaxseed, be sure to take it with a lot of water.

Possible interactions

Flaxseed supplements may alter the effects of some prescription and nonprescription medications. If you are currently being treated with any of the following medications, you should not use flaxseed without first talking to your doctor.

Blood-thinning medications -- Omega-3 fatty acids may increase the risk of bleeding, especially if you also take blood thinners such as warfarin (Coumadin), clopidogrel (Plavix), or aspirin. In some cases, the combination of aspirin and omega-3 fatty acids may be helpful. But they should not be taken together except under a doctor's supervision.

Medications for diabetes -- Flaxseed may lower blood sugar levels. If you are taking medicines for diabetes, including insulin, you should use flaxseed (ALA) only under your doctor's supervision.

Birth control pills or hormonal replacement therapy (HRT) -- Flaxseed may change hormonal levels and change the effects of oral contraceptives or HRT. If you are taking an oral contraceptive or undergoing HRT, ask your doctor before taking flaxseed.

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